In heat pump systems, existing refrigerant compensators are able to adjust refrigerant charge to accommodate different amounts of refrigerant that are needed during heating and cooling cycles. Since the optimum refrigerant charge during the cooling mode is different from the refrigerant charge during the heating mode, it is necessary to adjust the refrigerant charge to get better performance at the respective operating modes for heat pump applications. Existing charge compensators comprise a tank with a vapor tube passing directly through the tank. In the cooling mode, sub-cooled liquid refrigerant further cools down and is stored in the compensator due to heat transfer because the temperature of the refrigerant vapor passing through the compensator is lower than the sub-cooled liquid refrigerant. Conversely, in the heating mode, stored refrigerant is driven from the compensator because the stored refrigerant absorbs heat from the higher temperature vapor passing through the compensator.